ESTIMATION OF THE OCTANE NUMBER OF AUTOMOBILE GASOLINE BY FOURIER-TRANSFORM INFRARED-ABSORPTION SPECTROMETRY

A method to estimate the octane number of automobile gasoline by Fourier transform infrared absorption spectrometry has been studied. Thirty-six kinds of regular gasoline and 38 of unleaded premium gasoline, collected from the market from winter to summer, were used as samples, and the absorptions of the C-H stretching vibration in the 3150-2800 cm-1 range of their IR spectra were used to plot each sample in a two-dimensional space, followed by an attempt to graphically classify the two broad types. On the other hand, the IR spectra of other samples with known octane numbers (88.0 to 100.8 in octane number) and, on that basis, samples with known octane numbers, were mapped into the space in which the regular gasolines and the premium gasolines were classified to determine their dispersion in this space. A further attempt was made to formulate a linear regression equation for use in octane number estimation. As a result, it was found that regular and premium gasolines could be definitely distinguished from each other according to the C-H stretching vibration in the 3150-2800 cm-1 near-infrared range, and that the octane number could be visually estimated. The formulation of a satisfactory regression equation was also made possible. These results are reported.